1. Field of the Invention
The present invention relates to a seal member for an endless track of a construction vehicle, such as an excavator, a bulldozer or any other vehicle having an endless track.
2. Description of Related Art
As illustrated in FIG. 5, a M-shaped seal 14 for an endless track 10 of a vehicle is mounted between a bushing 11 and a bottom surface 13 of a counter bore of a link 12 of the endless track 10. The M-shaped seal 14 is configured to prevent debris such as water and mud from entering a clearance 16 between a pin 15 and the bushing 11 and to prevent a lubricant filling the clearance between the pin 15 and the bushing 11 from escaping or leaking.
Conventionally, the seal 14 of the endless track 10 has a cross section like alphabetical letter M (hereinafter, M-like seal) as illustrated in columns B of FIGS. 2–4. The M-like seal 14 is mounted between the bushing 11 and the bottom surface 13 of the counter bore of the link 12 with the centerline of letter M held transverse to an axial direction D of the bushing 11. The seal 14 can be compressed in the axial direction D of the bushing 11.
However, M-like seals can lead to uneven wear at certain portions thereof, which can shorten the life of such seals. Different examples of such wear will now be described.    (a) A contact pressure at the contact surface of the M-like seal 14 with the bushing 11 is not uniform (FIG. 6). As a result, wear proceeds more readily at a high-pressure portion of the contact surface than at other portions of the seal 14 (FIG. 7), and an uneven wear happens in the seal 14, which can shorten the life of the seal 14.    (b) When mounted to the endless track 10, a lip portion 17 of the M-like seal 14 is pushed by the bushing 11 to cause a space 18 at the contact surface of the seal 14 with the bushing 11. Mud is likely to enter the space 18 to cause wear to proceed (FIG. 8). When the wear proceeds, the lip 17 is further displaced in a direction away from the bushing 11 to cause more mud or debris to enter the space and to cause the uneven wear to proceed (FIG. 9). As a result, the life of the M-like seal 14 is further shortened.    (c) Since a wear margin of the M-like seal 14 at the contact surface of the seal with the bushing 11 is equal to or less than a thickness of a root 19 of a bushing-side leg of the M-like seal where the seal 14 contacts the bushing 11, the wear margin is small, and the life of the seal can be relatively short.